Image Credit: Jean Rajchenbach, Alphonse Leroux, and Didier Clamond (CNRS and Université de Nice, France)Snapshot of a wave with five-fold symmetry in a vibrating Newtonian liquid.

Waves at the surface of water are described by a set of nonlinear equations. These nonlinearities can induce the emergence of new patterns. In this experiment, a container partly filled with a Newtonian fluid is vibrated vertically. (Newtonian fluids include most common liquids and gases; examples are water and air.) The vibrations give rise to the formation of standing waves at the free surface of the fluid, a phenomenon known as the 'Faraday instability.'

This image shows a surface wave alternating in shape between a pentagon and a star. The order of the symmetry (in this case, five) can be varied according to the frequency and amplitude of the vibrations. Surprisingly, this number does not depend on the container's size or shape. The geometry of the standing wave can be interpreted as resulting from nonlinear resonant couplings between three waves.

This project has been partially supported by CNRS, Société ACRI and Région PACA.

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This image can be freely reproduced with the accompanying credit: "Jean Rajchenbach, Alphonse Leroux, and Didier Clamond (CNRS and Université de Nice, France)."